ERROR: Zend_Db_Statement_Exception: SQLSTATE[HY000]: General error: 23 Out of resources when open...

Hello,
I have a big problem. My plesk don't stop to crash. Completely random . Usually, once per day. When I try to connected me to my plesk, this error :
ERROR: Zend_Db_Statement_Exception: SQLSTATE[HY000]: General error: 23 Out of resources when opening file '/tmp/....' (Errcode: 24 "Too many open files") (Pdo.php:234)
(the file change everytime)

And all my sites using my database are out services. Other work.

I did the update 13, and she crashed, I have the impression that everything...

ERROR: Zend_Db_Statement_Exception: SQLSTATE[HY000]: General error: 23 Out of resources when open...